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haggen/prime.rb

Created May 27, 2011 16:20
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Find out if given number is prime
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prime.rb
#!/usr/bin/ruby
# Find out if given number is prime
# based on http://zmievski.org/2010/08/the-prime-that-wasnt by ANDREI ZMIEVSKI
# inspired by http://pastebin.com/PGT94gdF by MAURO BARALDI
def prime?(n)
n = '1' * n.to_i
n == '1' or !n[/^1?$|^(11+?)\1+$/]
end
puts prime?(ARGV[0]), "\n\n"
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